c_fopen.c

////////////////////////////////////////////////////////////////////////////////

#include <stdio.h>


// fopen - open a stream

void c_fopen_ ( FILE **fp, char *path, char *cmode )
{
   *fp = fopen ( path, cmode );
}

//
//
// New version: 
//    Pass arguments using its reference with value in integer(8), i.e.  
//    intptr_t defined in /usr/include/stdint.h
//

#include <stdint.h>

void  c_fopen_intref_ ( intptr_t *ifptr, char *path, char *cmode )
{
//
// Method 1: 
// FILE *fp ;  
// fp = fopen ( path, cmode );
// *ifptr = (intptr_t) (FILE *) fp  ;
//
// Or,
// Method 2:   
//
   *ifptr = (intptr_t) (FILE *) fopen ( path, cmode ) ; 
//
}




////////////////////////////////////////////////////////////////////////////////
/*
Ref:  
   https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html

#include <stdio.h>
   /usr/include/stdio.h
   +  fopen 
         FILE *fopen( const char *pathname, const char *cmode );

         The fopen() function shall open the file whose PATHNAME is the string 
      pointed to by PATHNAME, and associates a stream with it.

         The CMODE argument points to a string. If the string is one of the 
      following, the file shall be opened in the indicated mode. Otherwise, the 
      behavior is undefined.
         CMODE: 
         r or rb
            Open file for reading.
         w or wb
            Truncate to zero length or create file for writing.
         a or ab
            Append; open or create file for writing at end-of-file.
         r+ or rb+ or r+b
            Open file for update (reading and writing).
         w+ or wb+ or w+b
            Truncate to zero length or create file for update.
         a+ or ab+ or a+b
            Append; open or create file for update, writing at end-of-file. 

         Upon successful completion, fopen() shall return a pointer to the 
      object controlling the stream. Otherwise, a NULL pointer shall be 
      returned, and ERRNO shall be set to indicate the error. 

      EXAMPLES: Opening a File

         The following example tries to open the file named file for reading.
      The fopen() function returns a file pointer that is used in subsequent
      fgets() and fclose() calls. If the program cannot open the file, it just
      ignores it.

         #include <stdio.h>

         FILE *fp;

         void rgrep ( const char *file )
         {
            if ( (fp = fopen(file, "r")) == NULL )  return;
         }



      REMARKS: 

         'b':  The character 'b' shall have no effect, but is allowed for 
      ISO C standard conformance. 

         'r':  Opening a file with read mode (r as the first character in the 
      CMODE argument) shall fail if the file does not exist or cannot be read.

         'a':  Opening a file with append mode (a as the first character in the 
      CMODE argument) shall cause all subsequent writes to the file to be forced to 
      the then current end-of-file, regardless of intervening calls to fseek().

         '+':  When a file is opened with update mode ('+' as the second or third 
      character in the CMODE argument), both input and output may be performed on 
      the associated stream. However, the application shall ensure that output  
      is not directly followed by input without an intervening call to fflush() 
      or to a file positioning function (fseek(), fsetpos(), or rewind()), and 
      input is not directly followed by output without an intervening call to a 
      file positioning function, unless the input operation encounters end-of-file.

         When opened, a stream is fully buffered if and only if it can be 
      determined not to refer to an interactive device. The error and end-of-file
      indicators for the stream shall be cleared.

         If mode is w, wb, a, ab, w+, wb+, w+b, a+, ab+, or a+b, and the file 
      did not previously exist, upon successful completion, fopen() shall 

      +  mark for update the last data access, last data modification, and last 
         file status change timestamps of the file and the last file status 
         change and last data modification timestamps of the parent directory.

      +  create a file as if it called the creat() function with a value 
         appropriate for the path argument interpreted from pathname and a 
         value of S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH 
         for the CMODE argument.

      +  mark for update the last data modification and last file status change
         timestamps of the file.




      ERRNO:

         The fopen() function shall fail if:

         [EACCES]
            Search permission is denied on a component of the path prefix, or 
         the file exists and the permissions specified by mode are denied, or 
         the file does not exist and write permission is denied for the parent 
         directory of the file to be created.

         [EINTR]
            A signal was caught during fopen().

         [EISDIR]
            The named file is a directory and mode requires write access.

         [ELOOP]
            A loop exists in symbolic links encountered during resolution of 
         the path argument. 

         [EMFILE]
            All file descriptors available to the process are currently open.

         [EMFILE]
            {STREAM_MAX} streams are currently open in the calling process.

         [ENAMETOOLONG]
            The length of a pathname exceeds {PATH_MAX}, or pathname resolution
         of a symbolic link produced an intermediate result with a length that 
         exceeds {PATH_MAX}. 

         [ENFILE]
            The maximum allowable number of files is currently open in the system.

         [ENOENT]
            The mode string begins with 'r' and a component of pathname does not 
         name an existing file, or mode begins with 'w' or 'a' and a component of
         the path prefix of pathname does not name an existing file, or pathname
         is an empty string.

         [ENOENT] or [ENOTDIR]
            The pathname argument contains at least one non- <slash> character and
         ends with one or more trailing <slash> characters. If pathname without the
         trailing <slash> characters would name an existing file, an [ENOENT] error
         shall not occur. 

         [ENOSPC]
            The directory or file system that would contain the new file cannot be
         expanded, the file does not exist, and the file was to be created.

         [ENOTDIR]
            A component of the path prefix names an existing file that is neither
         a directory nor a symbolic link to a directory, or the pathname argument
         contains at least one non- <slash> character and ends with one or more
         trailing <slash> characters and the last pathname component names an 
         existing file that is neither a directory nor a symbolic link to a 
         directory. 

         [ENXIO]
            The named file is a character special or block special file, and the 
         device associated with this special file does not exist.

         [EOVERFLOW]
            The named file is a regular file and the size of the file cannot be 
         represented correctly in an object of type off_t. [Option End]

         [EROFS]
            The named file resides on a read-only file system and mode requires
         write access. 

         The fopen() function may fail if:

         [EINVAL]
            The value of the mode argument is not valid.

         [ELOOP]
            More than {SYMLOOP_MAX} symbolic links were encountered during 
         resolution of the path argument.

         [EMFILE]
            {FOPEN_MAX} streams are currently open in the calling process.

         [ENAMETOOLONG]
            The length of a component of a pathname is longer than {NAME_MAX}.

         [ENOMEM]
            Insufficient storage space is available.

         [ETXTBSY]
            The file is a pure procedure (shared text) file that is being 
         executed and mode requires write access. 


*/